The present invention relates to a connecting piece for a duct, preferably a ventilation duct, and comprising an inner flow space in communication with the interior of the duct, the connecting piece having at least one joining portion on which an end region of the duct is slidable and fixable.
The present invention also relates to a method of manufacturing a connecting piece intended for a duct, which is provided with an inner flow space and at least one joining portion for cooperation with the duct.
Finally, the present invention relates to a tool for manufacturing a connecting piece for a duct, and comprising a female union with a concave forming surface, the forming surface corresponding to the configuration of the outside of a shell body which forms part of the connecting piece, and a male union with a convex forming surface corresponding to the configuration of the inside of the shell body.
International Application PCT/SE2009/000281 discloses a ventilation duct which is produced from a compressed fiber material with a minor admixture of binder. The duct has longitudinal flexural lines in the corner regions, while the walls of the duct have transverse pivotal portions, rigidifying portions and relatively soft portions so that, in the unloaded or unstressed state, the duct displays a rectangular, possibly square cross section and is self-supporting across considerable lengths, up to between 2 and 3 m. Further, the duct is slightly flexible as a result of the presence of the relatively soft portions in the walls of the duct.
In one variation of the above-described duct, the duct has, on two opposing sides, been provided with longitudinal fold lines so that the cross-sectional configuration of the duct may thereby be modified from rectangular to hexagonal configuration. As a result, two opposing sides will be approximately twice as wide as the remaining four sides. Further, the cross-sectional configuration may vary so that it will be more or less flattened.
For interconnecting and joining duct sections of the above-outlined types, different types of connecting pieces are required, which may be straight connecting pieces of varying lengths, T-junctions, bends with different angles of curvature and radii, etc.
Those connecting pieces that are previously known in the art have been intended for ventilation ducts manufactured from sheet-metal material and consist of or comprise the same material themselves. This implies high manufacturing costs, often requirements on external insulation given the risk of condensation and needs for fire protection, and also probably considerable assembly- and sealing problems if they were to be used together with the above-described duct types.
It is desirable to design the connecting piece intimated by way of introduction such that it may be manufactured at low cost, that it inherently possesses a superior insulation property, that there are no fire hazards, and that simple assembly may be put into effect.
It is also desirable to design the method intimated by way of introduction such that the advantages inherent in the thus manufactured connecting piece will be attained.
It is also desirable to design the tool intimated by way of introduction such that it permits simple, rapid and economical manufacture, as well as adjustment of the tool for the manufacture of connecting pieces of different designs.
According to an aspect of the present invention, a connecting piece intimated by way of introduction is characterised in that the connecting piece includes a compressed fiber material and a binder, that the connecting piece displays a substantially configurationally stable portion in association with the joining portion, and that the connecting piece displays, at least interiorly, a layer which is impervious to a fluid, in particular a gas, this layer being adjacent the inner flow space of the connecting piece.
According to another aspect of the present invention, a method comprises the steps that two mirror-symmetric, possibly continuous shell bodies are produced by compression of a fiber material and a binder, that the shell bodies are provided with substantially configurationally stable portions in association with those portions that, in the finished state of the connecting piece, are to form the joining portion, that the shell bodies, at least on that side which, in the finished state of the connecting piece, is turned to face towards the flow space, is provided with a layer which is impervious to a fluid, in particular a gas, and that the shell bodies are united together.
According to yet another aspect of the present invention, a tool is characterised in that the forming surfaces are composed of edge surfaces on lamellae which are included in the female union and the male union.